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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<title>Boost.Range Terminology and Style Guidelines </title>
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<td ><img src="../../../boost.png" border="0" ></td>
<td ><h1 align="center">Boost.Range </h1></td>
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<h2>Terminology and style guidelines </h2>
<p>
The use of a consistent terminology is as important for <a href="range.html">Range</a>s
and range-based algorithms as it is for iterators and iterator-based algorithms.
If a conventional set of names are adopted, we can avoid misunderstandings and
write generic function prototypes that are <i>self-documenting</i>.
</p>
<p>
Since ranges are characterized by a specific underlying iterator type, we get a
type of range for each type of iterator. Hence we can speak of the following
types of ranges:
<ul>
<li>
<i>Value access</i> category:
<ul>
<li>
Readable Range
<li>
Writeable Range
<li>
Swappable Range
<li>
Lvalue Range
</ul>
<li>
<i>Traversal</i> category:
<ul>
<li>
<a href="range.html#single_pass_range">Single Pass Range</a>
<li>
<a href="range.html#forward_range">Forward Range</a>
<li>
<a href="range.html#bidirectional_range">Bidirectional Range</a> <li>
<a href="range.html#random_access_range">Random Access Range</a> </ul>
</ul>
Notice how we have used the categories from the <a href="../../iterator/doc/new-iter-concepts.html">new
style iterators</a>.
<p>
Notice that an iterator (and therefore an range) has one <i>traversal</i>
property and one or more properties from the <i>value access</i> category. So in
reality we will mostly talk about mixtures such as
<ul>
<li>
Random Access Readable Writeable Range
<li>
Forward Lvalue Range
</ul>
By convention, we should always specify the <i>traversal</i> property first as
done above. This seems reasonable since there will only be one <i>traversal</i>
property, but perhaps many <i>value access</i> properties.
</p>
<p>
It might, however, be reasonable to specify only one category if the other
category does not matter. For example, the <a
href="utility_class.html#iter_range">iterator_range</a> can be constructed from
a Forward Range. This means that we do not care about what <i>value access</i>
properties the Range has. Similarly, a Readable Range will be one that has the
lowest possible <i>traversal</i> property (Single Pass).
</p>
<p>
As another example, consider how we specify the interface of <code>std::sort()</code>.
Algorithms are usually more cumbersome to specify the interface of since both <i>traversal</i>
and <i>value access</i> properties must be exactly defined. The iterator-based
version looks like this:
<pre>
<span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>RandomAccessTraversalReadableWritableIterator </span><span class=special>>
</span><span class=keyword>void </span><span class=identifier>sort</span><span class=special>( </span><span class=identifier>RandomAccessTraversalReadableWritableIterator </span><span class=identifier>first</span><span class=special>,
</span><span class=identifier>RandomAccessTraversalReadableWritableIterator </span><span class=identifier>last </span><span class=special>);</span>
</pre>
For ranges the interface becomes
<pre>
<span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>RandomAccessReadableWritableRange </span><span class=special>>
</span><span class=keyword>void </span><span class=identifier>sort</span><span class=special>( </span><span class=identifier>RandomAccessReadableWritableRange</span><span class=special>& </span><span class=identifier>r </span><span class=special>);</span>
</pre>
</p>
<p>
</p>
<hr>
<p>
© <a name="Copyright" id="Copyright">Copyright</a> Thorsten Ottosen 2008.
</p>
<p>
Distributed under the Boost Software License, Version 1.0. (See
accompanying file LICENSE_1_0.txt or copy
at <a href=
"http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)
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